As a person moves about in a dry environment, electric charge accumulates on the

Question

As a person moves about in a dry environment, electric charge accumulates on the person's body. Once it is at high voltage, either positive or negative, the body can discharge via sparks and shocks. Consider a human body isolated from ground, with the typical capacitance 120 pF.

(a) What charge (in microCoulombs) on the body will produce a potential of 12.0 kV?

(b) Sensitive electronic devices can be destroyed by electrostatic discharge from a person. A particular device can be destroyed by a discharge releasing an energy of 275 µJ. To what voltage (in kV) on the body does this situation correspond?

Explanation / Answer

a)

Charge on the body is

Q=CV =(120*10-12)*(10*103)

Q=1.2*10-6 C or 1.2 uC

b)

Energy stored in capacitor is

E=(1/2)CV2

=>V=sqrt[2*E/C]=sqrt[2*(275*10-6)/(120*10-12)

V=23 452.0788 Volts = 23. 4520788kv

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